alertdialogの透明度の設定

Builder builder = new AlertDialog.Builder(getSherlockActivity());		
		builder.setTitle(title);
		builder.setPositiveButton(R.string.rating_continue,
				new DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialog, int whichButton) {
					}
				});
		builder.setNegativeButton(R.string.wispr_cancel,
				new DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialog, int whichButton) {
						/* User clicked cancel so do some stuff */
					}
				});
		
		final AlertDialog dialog = builder.create();
		dialog.show();
		
		Window window = dialog.getWindow();  
		WindowManager.LayoutParams lp = window.getAttributes();		
		lp.alpha = 0.8f;
		window.setAttributes(lp); 

Window window = dialog.getWindow();  
		WindowManager.LayoutParams lp = window.getAttributes();		
		lp.alpha = 0.8f;
		window.setAttributes(lp);